Methods for manufacturing SiC single crystals by solution methods, which are typically top seeded solution growth (TSSG) methods, maintain a temperature gradient in which the temperature falls from the lower section to the upper section in a Si solution in a graphite crucible, from the interior toward the solution surface. The C that has dissolved from the graphite crucible into the Si solution at the high temperature section at the bottom, primarily rides the convection current of the solution and rises, reaching the low temperature section near the solution surface and becoming supersaturated. By holding a SiC seed crystal at the tip of a support rod (graphite) and contacting the solution with the bottom side of the seed crystal as a crystal growth plane, a SiC single crystal grows from the supersaturated solution, on the crystal growth plane of the seed crystal.
For production of a SiC single crystal as a practical material, it is necessary to increase the growth rate to improve production efficiency. Increasing the growth rate requires a higher degree of supersaturation D of the solute, but if the degree of supersaturation D exceeds a certain fixed value Dc the growth boundary becomes “a roughened surface” and it becomes impossible to maintain flat growth for continuous uniform single crystal growth.
PTL 1, in particular, discloses that for growth of a single crystal semiconductor by a Czochralski crystal growth process, it is necessary to delay the growth rate to the target diameter via the diameter-enlarging process by tapered growth from the seed crystal.
Also, PTLs 2 and 3 disclose that periodically varying the lifting speed when a Si single crystal is grown from a Si molten liquid increases the production efficiency (PTL 1) or results in a uniform oxygen concentration in the plane (PTL 2), causing growth of a Si single crystal.
However, these all involve growth from a Si “molten liquid”, and merely utilize the fact that the molten liquid surface temperature is the melting point and that a Si single crystal grows by simply raising it to that height or greater, whereas they cannot be applied to methods in which a SiC single crystal grows by “supersaturation” of C from a Si—C “solution”.
Consequently, it has been desired to develop a method of growing a SiC single crystal by a solution method, in which it is possible to maintain flat growth that allows continuous uniform single crystal growth, while also improving the growth rate necessary for realizing high productivity.